New owner of a 1982 CB750K

[The Jimbonaut]

Good work bud, moving right along. I got the shim tool last week - all measured and will be working out what size shims to replace them with. Shooting for a 0.005" clearance across the board, and hoping that my local Honda dealer will have some shims that I can buy/swap out. Winterized my other ride (Yamaha V Star) yesterday and ticked another thing off the bucket list - riding in the snow. Gotta love Montreal.

 

[Eddiewo]

Love this thread, I recently bought an 82 cb750 and I'm just got my compression tester. waiting on a battery to hopefully pull decent numbers



Paul
1982 CB750k

 

[The Jimbonaut]

Nice one Paul, welcome to our figure-this-stuff-out-as-we-go-along thread =) And congrats on your new ride, got any pics? Let us know what numbers you pull on your tests and perhaps we can all help each other out!

I checked all my valve clearances and measured the shims - turned out I needed to adjust 9 shims (to get as closes to 0.005" as possible on exhaust and intake) but found I could switch out 4 of them. So I needed to buy 5 - called around my local Honda dealers all of whom could sell me brand new shims but only in the stock 0.05mm increments. Thing is, I needed sizes like 2.77mm. So I looked a bit further afield and found an old school Honda mechanic who's been working on vintage Japanese bikes for over 35 years - called him up and it turns out he has a bag of shims in every size, and he'd be happy to exchange with mine.

Definitely recommend doing this if you're looking for specific sized shims. He's a cool guy too and really knows his stuff, he also sold me 8 new cylinder head bolts as the rubber on my original ones had turned into plastic (from the engine heat) and were crumbling.

 

[SurferD]

Jim I sent you a message.

 

[The Jimbonaut]

Any luck contacting a local mechanic Surfer to see if they had any shims?

 

[SurferD]

Any luck contacting a local mechanic Surfer to see if they had any shims?

I tried but no one has any.
I was able to get some on ebay for about $4 each.
I need to measure them and see what else I need.
Keep in mind that the shims while stamped with a number aren't always accurate.
I took one out that said 2.975 but was actually 2.960.
So always measure with a good micrometer.
I have this one but it's overkill for most guys.
https://www.amazon.com/Mitutoyo-293...d=1480956145&sr=8-1&keywords=mitutoyo+293-185

 

[The Jimbonaut]

Cool, glad you got them sorted. My guy has a bunch but they're pretty random

 

[The Jimbonaut]

Hey man, how you getting on with your build?

 

[SurferD]

Hey man, how you getting on with your build?

Collecting shims and checking them twice.
I still need to source a few more.
It's hard getting the exact thickness needed.
I opened up my clearances but they are over a bit now.
.008-.009 so I will recalculate.

 

[The Jimbonaut]

Yeah, getting those clearances right was a heck of a job. Mine came in pretty good but it took a while. Good luck =)

I'm still waiting on a carb rebuild kit to arrive so working on the wheel bearings. Man, getting those suckers out was - how shall I say this - challenging? Let me know if you're changing your bearings and I can give you some pointers

 

[SurferD]

Yeah, getting those clearances right was a heck of a job. Mine came in pretty good but it took a while. Good luck =)

I'm still waiting on a carb rebuild kit to arrive so working on the wheel bearings. Man, getting those suckers out was - how shall I say this - challenging? Let me know if you're changing your bearings and I can give you some pointers

My bearings are fine. The bike only has 8443 miles and was always kept indoors so hopefully they won't need replacing for a while.
As for the rebuild kit, you need to read Mike Nixon's article about them.
http://www.motorcycleproject.com/text/carb_kits.html

 

[The Jimbonaut]

Read it, and bought his booklet =) I've emailed him loads too and he's always really quick to help. Great guy.

Good to hear your bearings are in great shape - getting those things out sucked.

 

[SurferD]

OK I finally sourced all the needed shims and got all valve clearances to .005-.007.
I performed a compression check and only got to about 100 in each cylinder.
I'ts pretty disappointing.

 

[The Jimbonaut]

When u were cranking the engine for the compression test, did u have the throttle wide open? Doing so could give u a better reading

 

[The Jimbonaut]

Otherwise (and I'm no expert) it could be u need new piston rings, or you could try blasting some sea foam into each carb's air intake with the engine running. You'll see a drop in rpm but throttle past that (around 5000rpm) - the sea foam might knock off carbon deposits in the cylinders and give you better compression.

Worked for me

 

[The Jimbonaut]

By the way, dotheton.com is worth joining if u haven't already. Busy forum, lots of help. I have a thread over there which may help you out as well, under Member Introductions. Just an idea

 

[SurferD]

Yea the carbs are off so there's no issue there.
The engine can't run and hasn't since I have owned it so far.

 

[The Jimbonaut]

Carbs were on when you ran the compression test?

 

[SurferD]

Carbs were on when you ran the compression test?

no they are off

 

[The Jimbonaut]

I'd get the carbs on the bike for sure. Otherwise you've got a big hole on each of the cylinders where the carbs should be - that'll surely affect the compression.

Try the test again, with the carbs connected to the cylinders, clamped on nice and tight. Soften up the rubbers first by warming them with a hair dryer (or soaking them in hot water for a while) - it'll make getting the carbs hooked up waaaaay easier. Don't ask me how I found that out...